Although N-[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]-3-trifluoromethylpyridine-2 -sulfonamide of the present invention is included in the substituted pyridinesulfonamide compounds widely expressed by a general formula of U.S. Pat. No. 4,435,206, it is not specifically disclosed in this U.S. patent.
U.S. Pat. No. 4,435,206 describes that N-(heterocyclicaminocarbonyl)pyridinesulfonamides are useful as a herbicide and discloses a number of specific compounds. But only N-[(4,6-dimethylpyrimidin-2-yl)aminocarbonyl]pyridine-2-sulfonamide is proven to have an activity against plants. The herbicidal activity of this compound is, however, still low as compared with that which is expected in practical use. Accordingly, this U.S. patent merely suggests that the N-(heterocyclicaminocarbonyl)pyridinesulfonamides may be used as a herbicide.
In order to develop a herbicide which can kill various noxious weeds at a small dosage, the present inventors have made extensive investigations about the relation between the chemical structure of such types of compounds of U.S. Pat. No. 4,435,206 and biological activity thereof and attained the present invention. That is, it has been found that a compound having an N-[(pyrimidin-2-yl)aminocarbonyl]pyridine-2-sulfonamide skeleton and having a trifluoromethyl group at the 3-position of the pyridine moiety thereof and a methoxy group at each of the 4- and 6-positions of the pyrimidine moiety thereof not only has a high herbicidal activity and a wide herbicidal spectrum as compared with the specific compound of the above-cited U.S. patent, the herbicidal effect of which was confirmed, as well as analogues thereof but also exhibits an excellent herbicidal effect against strongly noxious weeds which are considered to be difficultly controlled, such as purple nutsedge. Further, it has been found that the compound of the present invention is safe against tomato and turfs and can well control weeds which grow in the cultivation field of tomato or turfs, as compared with a number of analogues disclosed in U.S. Pat. No. 4,435,206.